package com.whu.endecrypt;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;


/**
 * @author Li Jiansong
 * @date:2015-7-14  上午10:20:58
 * @version :
 *
 */
public class AESUtil {
	//AES加密
	public static String encrypt(String seed,String clearText)//seed密钥，clearText明文
			throws Exception{
		byte[] rawKey=getRawKey(seed.getBytes());
		byte[] result=encrypt(rawKey, clearText.getBytes());
		return toHex(result);
	}
	//AES解密
	public static String decrypt(String seed, String encrypted)
			throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] enc = toByte(encrypted);
		byte[] result = decrypt(rawKey, enc);
		return new String(result);
		//return null;
	}

	private static byte[] getRawKey(byte[] seed)
			throws Exception{
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
      //  SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "Crypto"); 
		sr.setSeed(seed);
		kgen.init(128, sr); // 192 and 256 bits may not be available
		SecretKey skey = kgen.generateKey();
		byte[] raw = skey.getEncoded();
		return raw;
	}

	private static byte[] encrypt(byte[] raw, byte[] clear) 
			throws Exception{
		// TODO Auto-generated method stub
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
		byte[] encrypted = cipher.doFinal(clear);
		return encrypted;
		//return null;
	}

	private static byte[] decrypt(byte[] raw, byte[] encrypted)
			throws Exception {
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.DECRYPT_MODE, skeySpec);
		byte[] decrypted = cipher.doFinal(encrypted);
		return decrypted;
	}

	public static String toHex(String txt) {
		return toHex(txt.getBytes());
	}

	public static String fromHex(String hex) {
		return new String(toByte(hex));
	}

	private static byte[] toByte(String hexString) {
		// TODO Auto-generated method stub
		int len = hexString.length()/2;
		byte[] result = new byte[len];
		for (int i = 0; i < len; i++)
			result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
		return result;
	}

	public static String toHex(byte[] buf){
		if(buf==null){
			return "";
		}
		StringBuffer result=new StringBuffer(2*buf.length);
		for(int i=0;i<buf.length;i++){
			appendHex(result, buf[i]);
		}
		return result.toString();
	}
	
	private final static String HEX="0123456789ABCDEF";
	private static void appendHex(StringBuffer sb, byte b) {
		// TODO Auto-generated method stub
		sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));//charAt返回指定索引处的 char 值

	}

	/*-------------------------------*/
//	public static String getMD5Str(){
//		SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
//		return new MD5().getMd5(new Base64().getBase64(df.format(new Date())));
//	}
}
